Telecommunication transmission systems include both data and signaling channels arranged in repetitive frames whereby the signaling channels contain signaling information for the data channels. Over multiple frames, signaling information for all data channels is transmitted. According to at least one international transmission standard referred to as an E1 format which conforms to specifications set forth in CCITT draft recommendations G.703, G.704 and G.732, transmission frames consist of 32 channels, generally denoted as DSOs, each DSO containing 8 bits, and each 8 bits being referred to as a byte. Each frame contains a framing channel followed by 15 data channels followed by a signaling channel followed by a further group of 15 data channels. The signaling channel contains two groups of "ABCD" bits of information, and each group is referred to as a "nibble" herein, each nibble having 16 possible states for indicating signaling states for the data channels. The first ABCD nibble in the signaling channel indicates a signaling state for the first group of 15 data channels, with the second nibble representing 16 possible signaling states for the second group of 15 data channels within the frame, the two nibbles forming a signaling byte.
A problem exists in conveniently cross connecting the data and signaling channels contained in the local exchange frames between the telephone local exchange equipment and the distribution lines since the signaling information nibble associated with the first set of 15 data channels of a particular frame is located in the same channel as the signaling information nibble associated with the second set of 15 data channels of the same frame. Specifically, when reading out the DSO channel information into a cross connect memory using cross connect information in another memory, each frame has to be read out twice so that both nibbles can be appropriately accessed and addressed to an appropriate memory location. This requires that cross connect speed be doubled or that memory access speed be doubled over that which is otherwise necessary for reading into memory the data channels. In addition, means need to be provided for not disturbing an existing nibble in a signal memory when an additional signal nibble is being added to its DSO slot. Addressing these concerns complicates cross connect hardware and software in both a downstream and upstream transmission direction.